There exists an Open authentication (OAuth) protocol (see OAuth Specification 1.0 available at http://oauth.net/license/core/1.0) to handle user credentials between multiple parties on the web. Further, there exist a number of token-based sharing solutions that enable content sharing between web entities similar to the before mentioned OAuth system. For instance, Facebook, Flickr, Google, Smugmug and Photobucket all use tokens for authentication.